1. Field of the Invention
The present invention relates to a method for soldering a soft wire to a printed circuit board, and more particularly, relates to a method for soldering a magnet wire to a printed circuit board used for an electrical connector.
2. Description of the Prior Art
A high speed method of soldering insulated wire lying across a terminal pad of a circuit board coated with solder melting using a soldering tool is disclosed by Ronald in U.S. Pat. No. 4,484,054. The method includes the following steps: (a) selecting the effective mass of the soldering tool so that the quantum of heat energy stored therein when heated to a preselected high temperature is only slightly in excess of that required to vaporize insulation off the wire and to create an effective solder joint of solder melting at about 450.degree. F.; (b) heating the soldering tool of the selected mass to a preselected high temperature close to, but below, the temperature which would cause rapid deterioration of the tool; (c) bringing the soldering tool into contact with the insulated wire while lying across the solder coated terminal pad; (d) the quantum of heat energy in the tool being just sufficient (i) to vaporize insulation on the wire in the area of the contact point, (ii) to then vaporize the insulation on the side of the wire opposite to the contact point, and (iii) to then melt the solder on the solder coated terminal pad; (e) the quantum of heat energy being insufficient to permit significant heat migration into the circuit board or other components beyond the terminal pad; and (f) the total contact time for making the solder joint being less than 500 milliseconds.
Furthermore, a method to position the insulated wire across the terminal pad of a circuit board is also disclosed by above-mentioned Ronald patent. As shown in FIG. 1 of the Ronald patent, a circuit board is mounted for movement by an X-Y transport and is moved from point-to-point according to a computer control. A wire guide unit, scribing stylus and soldering tool are mounted above the circuit board so they can rotate as a unit. Insulated copper wire is fed through the wire guide toward stylus which presses the wire into the tacky surface coating on the circuit board as is best seen in FIG. 2 thereof. The rotational position of the scribing unit (including wire guide, stylus, and soldering tool) is determined in accordance with the direction of the table movement so that the wire is laid down on the board surface as the board moves away from the scribing unit.
However, this method needs much higher cost in equipments, such as a computer control. Furthermore, the wire guide and the stylus are not suited to position such a magnet wire that has a diameter even less than a hair.
Hence, a new method for soldering a soft wire to a printed circuit board conveniently is needed to solve the above problems.